linux-kernel - Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation

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Message-ID: <20220905204300.GC25951@gate.crashing.org>
Date:   Mon, 5 Sep 2022 15:43:00 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "aik@...abs.ru" <aik@...abs.ru>,
        "chenzhongjin@...wei.com" <chenzhongjin@...wei.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>
Subject: Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation

Hi!

On Mon, Sep 05, 2022 at 04:15:07PM +0530, Naveen N. Rao wrote:
> Segher Boessenkool wrote:
> >>> +		if ((insn & 3) == 1) {
> >>> +			*type = INSN_CALL;
> >>> +			*immediate = insn & 0x3fffffc;
> >>> +			if (*immediate & 0x2000000)
> >>> +				*immediate -= 0x4000000;
> >>> +		}
> >>> +		break;
> >>> +	}
> >
> >Does this handle AA=1 correctly at all?  That is valid both with and
> >without relocations, just like AA=0.  Same for AA=1 LK=0 btw.
> >
> >If you only handle AA=0, the code should explicitly test for that.
> 
> The code does test for AA=0 LK=1 with the if statement there?

Yes, but that is not what I said :-)

It may be fine to not *handle* AA=1 at all, but the code should at least
scream bloody murder when it encounters it anyway :-)


Segher